Use oslo.log library instead of system logging module

The constants of log levels were added in the 1.8 version of
the oslo.log library. So we can replace all usage of system
logging module with log module from oslo.log.

Change-Id: I2992df0bec6337aefa8a75d4853b132bd134fa42
Closes-Bug: 1481370
diff --git a/neutron/tests/tempest/config.py b/neutron/tests/tempest/config.py
index c459d76..200b247 100644
--- a/neutron/tests/tempest/config.py
+++ b/neutron/tests/tempest/config.py
@@ -15,7 +15,6 @@
 
 from __future__ import print_function
 
-import logging as std_logging
 import os
 
 from oslo_config import cfg
@@ -1191,7 +1190,7 @@
         register_opts()
         self._set_attrs()
         if parse_conf:
-            cfg.CONF.log_opt_values(LOG, std_logging.DEBUG)
+            cfg.CONF.log_opt_values(LOG, logging.DEBUG)
 
 
 class TempestConfigProxy(object):
@@ -1199,15 +1198,15 @@
     _path = None
 
     _extra_log_defaults = [
-        ('keystoneclient.session', std_logging.INFO),
-        ('paramiko.transport', std_logging.INFO),
-        ('requests.packages.urllib3.connectionpool', std_logging.WARN),
+        ('keystoneclient.session', logging.INFO),
+        ('paramiko.transport', logging.INFO),
+        ('requests.packages.urllib3.connectionpool', logging.WARN),
     ]
 
     def _fix_log_levels(self):
         """Tweak the oslo log defaults."""
         for name, level in self._extra_log_defaults:
-            std_logging.getLogger(name).setLevel(level)
+            logging.getLogger(name).logger.setLevel(level)
 
     def __getattr__(self, attr):
         if not self._config: